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UNIVERSITY  OF  ILLINOIS 

Agricultural  Experiment  Station 


BULLETIN  NO.  284 


THE  INFLUENCE  OF  PLANT 

INJURY  AND  THE  ROOT  ROT  DISEASES 

UPON  THE  PHYSICAL  AND  CHEMICAL 

COMPOSITION  OF  CORN  GRAIN 


BY  GEORGE  H.  DUNCAN 


URBANA,  ILLINOIS,  DECEMBER,  1926 


SUMMARY 

Constricting  the  ear-shanks  and  stalks  of  corn  by  breaking  the 
supporting  tissue  in  these  structures  without  completely  severing  the 
vascular  elements  had  essentially  the  same  effect  upon  the  yield  and 
composition  of  corn  grain  as  premature  harvesting.  Constriction  of  the 
shank  was  much  more  detrimental  to  ear  development  than  the  break- 
ing of  the  stalk. 

Breaking  the  shanks  when  the  ears  were  in  the  soft-dough  stage 
caused  the  greatest  degree  of  chaffiness  in  the  grain.  Chemical  analy- 
ses showed  that  there  was  no  definite  correlation  between  kernel 
"starchiness"  and  quantity  of  starch  in  the  grain,  as  has  been  com- 
monly supposed.  In  fact  the  quantity  of  true  starch  was  often  less  in 
the  "starchy"  than  in  the  horny  grain.  In  the  light  of  these  results  it 
is  suggested  that  the  term  "floury"  be  substituted  for  the  word 
"starchy"  in  describing  the  corn  containing  more  than  a  normal  quan- 
tity of  soft,  dry,  friable  material. 

The  percentage  of  total  nitrogen,  hemicellulose,  and  non-hydro- 
lyzable  material  was  distinctly  higher  in  grain  from  ears  produced  on 
broken  shanks  than  in  grain  from  ears  produced  on  sound  shanks.  The 
mutilation  of  the  shanks,  on  the  other  hand,  resulted  in  a  greatly  re- 
duced proportion  of  ether  extract  and  starch  in  the  grain. 

Inoculation  of  the  seed  at  planting  time  with  corn  root  rot  organ- 
isms resulted  in  the  production  of  grain  having  a  specific  gravity  .027 
lower  than  that  from  the  adjoining  uninoculated  plants. 

The  samples  of  grain  produced  by  plants  that  grew  in  the  inocu- 
lated hills  absorbed  an  average  of  5.78  percent  more  water  than  the 
samples  from  plants  growing  in  uninoculated  hills,  with  odds  .greater 
than  9999  to  1  that  this  difference  was  not  due  to  chance. 

Chemical  analyses  did  not  show  any  significant  differences  be- 
tween the  grain  produced  in  the  inoculated  and  uninoculated  hills. 
There  was  slightly  more  nitrogen,  on  the  average,  in  the  corn  from  in- 
oculated seed,  and  a  little  less  ether  extract  and  total  sugar.  Even 
tho  the  average  differences  in  total  nitrogen,  ether  extract,  and  total 
sugar  were  not  large,  the  odds  indicating  the  significance  of  these  re- 
sults were  above  30  to  1. 

Analyses  of  two  lots  of  horny  and  two  lots  of  floury  corn  of  the 
Learning  variety  showed  that  there  was  no  significant  distinction  in 
chemical  composition  between  these  two  types  of  corn.  Upon  germi- 
nation, however,  the  horny  corn  was  found  to  contain  a  greater  pro- 
portion of  soluble  starch  and  dextrins  than  the  floury  corn,  and  starch 
digestion  in  the  horny  corn  was  somewhat  more  rapid  than  in  the 
floury  corn.  This  phenomenon  offers  an  explanation  for  the  superior 
vigor  of  seedlings  from  horny  corn,  so  frequently  observed. 


THE  INFLUENCE  OF  PLANT 

INJURY  AND  THE  ROOT  ROT  DISEASES 

UPON  THE  PHYSICAL  AND  CHEMICAL 

COMPOSITION  OF  CORN  GRAIN 

By  GEORGE  H.  DUNCAN,  Assistant  Chief  in  Crop  Production 

INTRODUCTION 

For  a  number  of  years  the  Illinois  Agricultural  Experiment  Sta- 
tion has  advised  farmers  to  eliminate  all  extremely  "starchy"  ears  from 
their  seed  stock.  This  recommendation  has  been  based  upon  the  re- 
sults of  investigations  into  the  causes  of  the  corn  rot  diseases  obtained 
by  the  Station  and  the  Office  of  Cereal  Investigations  of  the  U.  S.  De- 
partment of  Agriculture  working  cooperatively. 

In  these  investigations  by  Holbert  and  associates13  the  fact  is 
established  that  a  high  degree  of  correlation  exists  between  certain  ear 
characters  in  seed  corn  and  susceptibility  of  seedlings  developed  from 
such  ears  to  infection  by  root  rot  organisms.  They  give  the  important 
diagnostic  features  of  diseased  seed  corn  as:  (a)  a  lack  of  luster 
in  the  ear;  (b)  a  discolored  or  shredded  shank  attachment;  (c)  a 
bleached  ear  tip;  (d)  an  extremely  deep  indentation  at  the  crown 
of  the  kernel ;  (e)  a  relatively  high  proportion  of  soft  to  horny  starch 
in  the  endosperm;  and  (f)  a  dull  wrinkled  kernel,  especially  in  the 
region  of  the  germ.  It  is  evident  that  these  characters  are  not  en- 
tirely independent  of  one  another,  for  an  increased  percentage  of  soft 
starch  in  the  endosperm  tends  to  decrease  the  luster  of  the  ear,  and  a 
high  content  of  soft  starch  is  often  accompanied  also  by  deep  kernel 
indentation.  Thus  it  would  seem  that  the  composition  of  the  grain, 
especially  the  proportion  of  soft  to  horny  starch  in  the  endosperm,  is 
a  very  important  factor,  if  not  the  most  important  single  factor,  in 
determining  susceptibility  or  resistance  to  disease,  or  at  least  in  indi- 
cating such  susceptibility  or  resistance.  The  data  from  one  experiment 
in  which  horny  and  "starchy"  kernels  were  selected  from  the  same  ears 
and  grown  in  comparative  yield  trials,  showed  a  reduction  of  12  bush- 
els an  acre  for  the  "starchy"  seed.  The  results  of  investigations  over 
a  period  of  seven  years  showed  a  decrease  of  7.9  bushels  an  acre  for 
"starchy"  seed,  with  odds  greater  than  one  million  to  one  that  this 
difference  was  not  the  result  of  chance. 

Trost38  found  that  ears  of  the  "starchy"  class  were  character- 
ized by  a  larger  percentage  of  infection  on  the  germinator  than  horny 

255 


256  BULLETIN  No.  284  [December, 

ears  from  the  same  seed  sample.  In  experiments  using  Reid  Yellow 
Dent  corn  as  seed,  the  "starchy"  ears  produced  a  larger  number  of 
weak  plants  and  14  percent  lower  yield  than  did  ears  less  "starchy"  in 
composition. 

No  data,  however,  have  as  yet  been  obtained  as  to  why  corn  con- 
taining a  large  proportion  of  soft  starch  is  more  susceptible  to  fungus 
invasion  than  corn  containing  a  smaller  proportion,  and  very  little  di- 
rect knowledge  is  available  as  to  the  factors  that  influence  the  physical 
composition  of  the  endosperm  in  corn  grain.  In  general  it  may  be  said 
that  the  agencies  which  determine  the  type  of  endosperm  in  corn 
divide  themselves  into  two  classes;  namely,  hereditary  factors,  and 
those  factors  that  may  be  included  under  the  general  term  environ- 
ment. The  present  work  has  been  confined  to  a  study  of  certain  fact- 
ors in  the  second  group ;  namely,  the  influence  that  stalk  and  shank  in- 
jury may  have  at  two  different  stages  in  the  development  of  the  ear, 
and  the  effect  of  the  inoculation  of  the  seed  at  planting  time  with  four 
organisms,  viz.,  Diplodia  zeae  (Schw.)  Lev.,  Fusarium  moniliforme 
Sheldon,  Gibberella  saubinetii  (Mont.)  Sacc.,  and  Rhizopus  spp.,  any 
one  of  which  is  capable  of  producing  a  corn  root  rot  disease.  Data 
are  also  presented  on  the  comparative  chemical  composition  of  starchy 
and  horny  kernels  at  different  stages  during  the  process  of  germination. 

REVIEW  OF  LITERATURE 

The  literature  reporting  the  influence  of  ecological  factors  on  the 
physical  and  chemical  composition  of  cereal  grains  is  voluminous,  and 
this  summary  is  not  presented  as  in  any  sense  exhausting  that  general 
subject.  Only  those  papers  are  reviewed  that  show  the  influence  of 
the  stage  of  harvesting  and  plant  injury  from  mechanical  or  parasitic 
causes  on  the  composition  of  the  grain. 

The  monumental  researches  of  Hornberger15  in  1882  constitute 
one  of  the  most  intensive  pieces  of  work  on  the  corn  plant  up  to  that 
time.  Later  Schweitzer,28  Jones  and  Huston,18  and  Smith,32  engaged  in 
the  study  of  the  same  problem.  These  workers  agreed  with  Horn- 
berger,18 who  found  that  as  the  grain  developed  beyond  the  milk  stage 
the  proportion  of  ether  extract  increased,  while  the  percentage  of 
total  nitrogen  and  ash  decreased.  They  also  noted  that  the  relative 
amount  of  carbohydrates  increased  with  maturity,  while  that  of  the 
crude  fiber  decreased.  The  investigations  of  Ince17  also  showed  a  larger 
proportion  of  crude  fat  and  nitrogen-free  extract  in  mature  grain  than 
in  immature  grain.  Bushey3  reported  that  corn  cut  short  in  its  devel- 
opment by  frost  contained  higher  percentages  of  ash  and  crube  fiber 
than  unfrosted  corn.  A  comparatively  high  proportion  of  the  nitrogen 
of  the  soft  corn  was  in  the  amid-albumin  and  globulin  forms.  Hume, 
Champlin,  and  Loomis16  noted  that  completely  mature  corn  contained 


1926}  INFLUENCE  OF  PLANT  INJURY  ON  COMPOSITION  OF  CORN  257 

the  largest  percentage  of  oil.  Appleman1  found  that  the  grain  of  sweet 
corn  decreased  markedly  in  content  both  of  total  sugar  and  of  reducing 
sugar  as  it  developed  from  the  milk  to  the  dough  stage.  Kent,  Patrick, 
Eaton,  and  Heileman20  and  Curtiss  and  Patrick6  found  that  after  the 
ears  had  reached  the  dough  stage  there  was  but  little  change  in  the 
composition  of  the  grain,  altho  there  was  a  gain  in  yield  per  acre. 

Analyses  reported  by  Saunders27  showed  that  there  was  a  rapid 
reduction  in  proportion  of  crude  protein  in  the  wheat  grain  during  its 
early  development,  and  that  afterwards  there  was  a  gradual  percent- 
age increase  in  this  material.  Similar  results  were  also  obtained  by 
McDowell25  in  both  winter  and  spring  wheat,  altho  the  percentage  in- 
crease in  protein  following  the  early  rapid  decrease  was  fluctuating  in 
character. 

LeClerc21  working  with  wheat,  and  Failyer  and  Willard10  work- 
ing with  both  oats  and  wheat,  found  that  late  cutting  resulted  in  a 
slightly  reduced  proportion  of  nitrogen  in  the  grain. 

Kedzie19  made  analyses  of  wheat  grain  at  a  great  many  stages,  be- 
ginning when  the  heads  were  just  past  the  "blossom"  stage  and  con- 
tinuing until  the  grain  was  dead  ripe  and  the  straw  fallen.  His  data 
showed  a  decrease  in  the  percentage  of  ash  and  crude-fiber  content  as 
the  grain  matured.  The  relative  amounts  of  albuminoids  and  amid 
nitrogen  decreased  rapidly  up  to  the  hard-dough  stage,  after  which 
they  increased  slightly.  The  proportion  of  ether  extract  decreased  un- 
til the  grain  was  in  the  milk  stage,  after  which  it  rose  gradually.  The 
percentage  of  nitrogen-free  extract  increased  up  to  the  hard-dough 
stage,  then  dropped  off  slightly. 

Data  presented  by  Shutt31  indicated  that  wheat  grain  injured  by 
frost  before  it  was  completely  mature  contained  a  lower  percentage  of 
both  total  nitrogen  and  albuminoid  nitrogen.  Blish2  reported  that 
"frozen  wheat  contains  larger  amounts  of  non-protein  nitrogen,  reduc- 
ing sugars,  and  acid-reacting  constituents  than  does  sound  wheat.  The 
non-protein  nitrogen  of  the  frozen  wheat  carries  a  considerably  higher 
percentage  of  a-amino  nitrogen  than  that  of  sound  wheat." 

Severe  rust  injury  hastened  the  ripening  of  wheat,  and  according 
to  Shutt30  markedly  increased  the  percentage  of  protein,  crude  fiber, 
and  ash,  and  lowered  the  proportion  of  fat  and  nitrogen-free  extract. 
Similar  results  as  to  the  effect  of  rust  on  the  ash  and  protein  contents 
of  the  wheat  grain  were  obtained  by  Stoa.35  Headden,12  however, 
stated  that  the  shrunken  berries  resulting  from  rust  infection  were  not 
high  in  protein.  He  pointed  out  that  protein  and  starch  were  laid 
down  simultaneously,  and  the  effect  of  rust  was  to  prevent  the  transfer 
of  the  filling  material  to  the  berries. 

Microchemical  studies  by  Eckerson9  indicated  that  starch  was 
formed  in  the  endosperm  cells  of  the  developing  wheat  grain  soon  after 
the  formation  of  the  cell  walls,  and  that  this  process  continued  until 


258  BULLETIN  No.  284  [December, 

desiccation  began.  Storage  proteins  were  not  formed  in  the  endosperm 
until  the  drying  of  the  grain  caused  the  amino  acids  present  to  con- 
dense into  proteins. 

MATERIALS  AND  METHODS 

In  the  experiment  to  determine  the  effect  of  breaking  the  stalks 
and  ear-shanks,  yellow  dent  corn  obtained  from  James  R.  Holbert  of 
the  U.  S.  Department  of  Agriculture,  was  used  as  seed.  It  was  of  F^ 
hybrid  material  between  pure-line  strains,  and  consequently  was  much 
more  uniform  in  genetic  constitution  than  average  open-pollinated 
corn.  Seed  of  this  corn  was  planted  on  the  University  South  Farm 
and  received  the  usual  cultivation  under  field  conditions. 

On  August  17,  when  the  grain  was  in  the  "milk"  stage,  and  also  on 
August  31,  after  the  grain  had  reached  the  "soft-dough"  stage,  a  num- 
ber of  the  ears  were  broken  down  to  the  extent  of  markedly  constrict- 
ing the  supporting  shank  but  not  severing  the  ear  from  the  stalk.  Also, 
on  these  two  dates,  a  number  of  plants  were  broken  over,  so  that  a 
definite  constriction  resulted  between  the  nodes  of  the  stalk  about  one 
foot  from  the  surface  of  the  ground.  The  grain  from  plants  so  treated 
was  analyzed  and  the  results  compared  with  similar  data  from  ears 
produced  on  plants  which  had  not  been  mutilated. 

The  seed  used  in  the  experiment  to  determine  the  effect  of  plant 
infection  with  corn  root,  stalk,  and  ear  rot-producing  organisms  on  the 
composition  of  the  grain  was  obtained  from  the  Plant  Breeding  Divi- 
sion of  the  University  of  Illinois.  This  seed  had  been  inbred  for  two 
generations.  Two  ears  possessed  an  extremely  horny  endosperm  and 
two  an  endosperm  containing  a  high  proportion  of  soft  starch.  These 
were  planted  on  May  16,  in  soil  that  had  grown  alfalfa  for  the  twelve 
years  prior  to  this  corn  crop.  At  the  time  of  planting,  the  alternate 
hills  were  inoculated  with  a  pure  culture  of  some  one  of  the  following 
organisms:  Diplodia  zeae  (Schw.)  Lev.,  Fusarium  monitiforme  Shel- 
don, Gibberella  saubinetii  (Mont.)  Sacc.,  and  Rhizopus  spp.  The 
grains  were  laid,  germs  up,  in  the  hill.  Two  horny  kernels  were  placed 
about  an  inch  apart  on  the  north  side  of  the  hill  and  two  "starchy" 
kernels  were  similarly  placed  on  the  south  side  of  the  hill.  Two  drops 
of  a  heavy  spore  suspension  of  one  of  the  above-mentioned  organisms 
were  placed  on  the  germ  face  of  each  kernel  in  the  alternate  hills.  In 
order  to  make  sure  of  getting  an  infection  with  Diplodia  zeae  a  frag- 
ment of  shredded  cornstalk  bearing  a  pure  culture  of  this  organism 
was  placed  between  the  kernels  in  the  hill  in  addition  to  the  spore  sus- 
pension placed  on  the  kernels.  Two  drops  of  distilled  water  were  placed 
on  the  germ  face  of  each  kernel  in  the  uninoculated  hills.  After  the 
moisture  in  the  drops  of  spore  suspension  had  partially  dried  down, 
the  corn  was  covered  with  moist  soil  which  was  pressed  firmly  down 
over  the  seed. 


1926]  INFLUENCE  OF  PLANT  INJURY  ON  COMPOSITION  OF  CORN  259 

The  cultures  of  Fusarium  moniliforme  and  Rhizopus  spp.  were  iso- 
lated from  germinating  corn.  The  cultures  of  Diplodia  zeae  and  Gib- 
berella  saubinetii  (the  latter  designated  as  strain  259)  were  obtained 
from  Miss  Helen  Johann,  of  the  U.  S.  Department  of  Agriculture. 

In  the  study  of  the  progressive  chemical  changes  occurring  dur- 
ing germination  in  horny  corn,  as  compared  with  those  occuring  in 
"starchy"  corn,  the  Learning  variety  was  used.  This  lot  of  corn  con- 
sisted of  twelve  ears,  six  of  which  were  smoothly  indented  and  high 
in  percentage  of  horny  starch  and  six  of  which  were  rough  in  indenta- 
tion and  relatively  high  in  soft  starch.  All  of  these  ears  had  been 
carefully  field-selected  early  in  November  and  were  alike  in  that  they 
had  all  been  produced  on  apparently  healthy  plants. 

These  ears  were  divided  into  four  lots  of  three  ears  each.  Lots  A 
and  C  were  made  up  of  horny  ears,  and  Lots  B  and  D  of  "starchy" 
ears  (Figs.  1  and  2). 

Five  sets  of  germination  tests  were  started  in  the  temperature- 
control  chamber,  which  was  maintained  at  16°  C.  in  the  plant  pathol- 
ogy greenhouse  at  the  University  of  Wisconsina.  Each  test  contained 
20  kernels  from  each  ear,  the  kernels  in  each  case  being  removed  from 
the  same  rows  on  the  ear.  The  corn  was  germinated  between  muslin 
cloths  over  moist  sand.  At  the  end  of  the  2d,  4th,  6th,  8th,  and  10th 
days  a  set  of  the  tests  was  removed  and  the  kernels  or  seedlings  dried 
for  analysis.  Drying  was  effected  by  placing  the  samples  in  the  oven 
at  100°  C.  for  one  hour  to  kill  the  enzyms,  followed  by  18  hours  of 
drying  with  the  oven  door  open  (Link  and  Tottingham22) . 

CHEMICAL  METHODS 

All  samples  of  corn  grain  analyzed  were  finely  ground  and  passed 
thru  a  100-mesh  sieve.  The  total  nitrogen  determinations  were  made 
by  the  Official  Gunning  method  modified  to  include  the  nitrogen  of 
nitrates.7  The  soluble  nitrogen  was  extracted  by  soaking  the  ground 
grain  for  four  hours  in  50  cc.  of  distilled  water  to  each  gram  of  sample. 

The  sugars  were  extracted  from  the  ether-extract-free  sample  with 
90  percent  ethyl  alcohol,  by  gently  boiling  the  sample  for  one  hour. 
After  the  alcohol  was  evaporated,  the  sirupy  residue  was  taken  up  with 
water  and  the  solution  clarified  with  neutral  lead  acetate.  The  excess 
lead  acetate  in  the  filtrate  was  then  removed  by  adding  sodium  sulfate 
and  sodium  carbonate  in  the  proportion  of  nine  parts  of  the  former  to 
one  of  the  latter.  Phenolphthalein  was  used  to  indicate  when  defeca- 
tion was  complete.  After  filtering,  the  reducing  sugar  was  determined, 
an  aliquot  of  the  clear  filtrate  being  used  for  this  purpose.  Total  su- 
gars were  determined  after  hydrolysis  in  2.5-percent  hydrochloric  acid, 
by  boiling  on  a  sand  bath  for  one  hour. 


"All  the  germinative  tests  and  chemical  analyses  in  this  investigation  were 
made  at  the  University  of  Wisconsin. 


260 


BULLETIN  No.  284 


[December, 


FIG.  1. — HORNY  EARS  OP  LEAMING  CORN  USED  IN  STUDY  OF  CHEMICAL 

CHANGES  OCCURRING  DURING  GERMINATION 

Kernels  from  these  two  lots  of  horny  corn  and  from  two  lots  of 
"starchy"  corn  (Fig.  2)  were  germinated,  and  the  chemical  changes 
taking  place  during  germination  were  determined  by  analyzing  samples 
taken  at  two-day  intervals.  The  results  are  described  on  pages  269 
to  275. 


Dextrins  and  soluble  starch  were  extracted  with  cold  water  in 
which  the  sugar- free  sample  was  allowed  to  soak  overnight.  The  fil- 
trate was  hydrolyzed  by  boiling  in  2.5-percent  hydrochloric  acid  for 
2Y2  hours. 

The  solution  containing  the  insoluble  starch  was  boiled  for  three 
minutes  to  gelatinize  the  starch  present.  When  cooled  to  38°  C.,  fresh 
saliva  was  added  to  hydrolyze  the  starch  to  maltose.  The  complete 
conversion  of  starch  to  maltose  was  indicated  by  failure  of  the  mater- 
ial to  give  a  blue  color  with  iodin.  The  maltose  extract  was  hydro- 
lyzed to  glucose  by  adding  hydrochloric  acid  until  the  concentration 
of  the  acid  in  the  solution  was  2.5  percent  and  by  boiling  over  a  sand 
bath  for  2%  hours. 

The  residue  was  washed  into  a  flask  and  submitted  to  hydrolysis 
in  2.5-percent  hydrochloric  acid  for  one  hour.  The  filtrate  was  consid- 
ered to  be  hemicellulose. 


1926}  INFLUENCE  OF  PLANT  INJURY  ON  COMPOSITION  OF  CORN 


261 


FIG.  2. — "STARCHY"  EARS  OF  LEAMING  CORN  USED  IN  THE 

GERMINATION  STUDY 

The  relative  proportion  of  horny  and  soft  starch  in  these  ears  is 
.indicated  by  the  transverse  and  longitudinal  sections  of  the  grain.  A 
preliminary  analysis  showed  practically  the  same  percentage  composi- 
tion for  both  horny  and  "starchy"  lots,  but  their  specific  gravity  was 
markedly  different. 


The  quantity  of  sugars,  soluble  starch,  and  dextrins,  insoluble 
starch,  and  hemicellulose  was  ascertained  by  determining  the  power  of 
these  substances  to  reduce  the  copper  of  Fehling's  solution.  The 
amount  of  copper  reduced  was  measured  by  the  Shaffer-Hartman29 
iodometric  titration  method. 

EXPERIMENTAL  RESULTS 
EFFECT  OF  BROKEN  STALK  AND  EAR  SHANKS 

Weak  and  diseased  corn  plants  are  frequently  not  strong  enough 
to  support  the  ears  to  complete  maturity ;  the  increasing  weight  of  the 
ear  may  exceed  the  strength  of  the  supporting  tissue  of  the  shank,  or 
the  stalk  itself  may  be  deficient  in  mechanical  substance  and  break 
over  under  stress  of  wind.  To  simulate  what  so  often  happens  in  na- 


262 


BULLETIN  No.  284 


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1926} 


INFLUENCE  OF  PLANT  INJURY  ON  COMPOSITION  OF  CORN 


263 


ture,  a  number  of  ear  shanks  and  cornstalks  were  artificially  broken 
on  August  17,  when  the  grain  was  in  the  milk  stage,  and  on  August  31, 
when  the  grain  was  in  the  soft-dough  stage. 

The  breaking-over  of  the  stalks  and  ear  shanks  did  not  in  any 
case  involve  the  complete  severance  of  the  ear  from  the  shank,  nor  of 
the  upper  portion  of  the  stalk  from  the  stub.  The  vascular  elements, 
or  at  least  most  of  them,  remained  intact.  There  was,  however,  a  dis- 
tinct constriction  produced,  which  doubtless  interfered  greatly  with 
the  translocation  of  reserve  and  building  materials  to  the  ear.  It  would 
seem  that  the  constriction  of  the  shank,  brought  about  by  breaking 
down  the  ears,  would  be  greater  than  that  of  the  stalk,  owing  to  the 
fact  that  the  break  caused  a  departure  of  approximately  120°  from 
the  normal  position  of  the  shank,  whereas  the  break  of  the  stalk  re- 
sulted in  a  declination  of  only  a  little  over  90°. 

That  the  constriction  of  the  shank  and  stalk  produced  a  marked 
effect  upon  the  size  and  character  of  the  ears  and  kernels  may  be  ob- 
served by  reference  to  Fig.  3  and  by  a  study  of  the  data  presented  in 
Table  1. 

The  breaking  of  the  ear-shank  produced  a  much  greater  hindrance 
to  the  proper  filling  of  the  grain  than  the  constriction  of  the  stalk. 
This  is  particularly  pronounced  in  the  weight  of  ears,  the  weight  of 


TABLE  I.-W-EFFECT  OF  BREAKING  THE  SHANKS  AND  STALKS  OF  CORN  ON  WEIGHT  OF 
EARS  (GRAIN  AND  COB),  WEIGHT  OF  TEN  KERNELS  FROM  EACH  EAR,  AND 
GERMINATIVE  VIGOR  OF  THE  KERNELS 


Average 

Average 

length  of 

Group 

Treatment 

Average 
weight 
of  ears 

Average 
weight 
of  10 
kernels 

Average 
germi- 
nation in 
soil 

number 
of  secon- 
dary 
roots 
per  seed- 

plumule 
at  end  of 
8-day 
germi- 
nation 

ling 

test  in 

soil 

grams 

grams 

perct. 

mm. 

A 

Parent  ears  

2.96 

98.0 

2.88 

120 

B 

Shank  broken  when  grain 

was  in  milk  stage  

78.4 

.69 

52.3 

1.60 

74 

C 

Shank  broken  when  grain 

was  in  soft-dough  stage  .  . 

191.8 

1.59 

97.1 

1.65 

75 

D 

Stalk  broken  when  grain 

was  in  milk  stage  

272.4 

2.37 

88.1 

2.67 

87 

E 

Stalk  broken  when  grain 

was  in  soft-dough  stage  .  . 

261.0 

2.38 

88.3 

2.96 

100 

F 

Ears  from  erect  plants  and 

from  unbroken  shanks  .  .  . 

331.1 

2.86 

98.1 

3.43 

117 

264 


BULLETIN  No.  284 


[December, 


ten  kernels,  the  number  of  secondary  roots,  and  the  length  of  plumules. 
Even  tho  the  delay  in  breaking  the  shanks  until  the  soft-dough  stage 
resulted  in  a  much  greater  weight  of  ear  and  kernel,  and  also  increased 
the  percentage  of  germination,  the  vigor  of  the  seedlings  produced  by 
this  corn,  as  measured  by  number  of  secondary  roots  and  length  of 
plumule,  was  only  very  slightly  better  than  that  of  the  corn  the  shanks 
of  which  were  broken  when  the  grain  was  in  the  milk  stage. 

The  chaffy  character  of  the  ears  in  Group  C,  Fig.  3,  is  striking. 
All  the  ears  in  this  experiment  that  had  their  shanks  broken  when  the 
grain  was  in  the  soft-dough  stage  contained  a  very  high  proportion  of 
soft  starch.  A  comparison  of  the  various  lots  of  ears  in  respect  to  the 
relative  quantity  of  soft  and  horny  starch  in  the  endosperm  of  the 
kernels  is  afforded  in  Table  2. 

The  parent  ears  and  those  that  matured  on  erect  plants  and  on 
unbroken  shanks  contained  the  highest  percentage  of  horny  and  the 


TABLE  2. — EFFECT  OF  BREAKING  THE  SHANKS  AND  STALKS  OF  CORN  AT  Two 

DIFFERENT  STAGES  OF  GROWTH,  ON  THE  KERNEL  CHARACTER 

OF  THE  EARS  PRODUCED 


Group 

Treatment 

Number 
of  ears 
repre- 
sented 

Kernel  character: 
percentage  of  ears  that  were 

Horny 

Medium 

Starchy 

A 
B 

C 
D 
E 
F 

Parent  ears  

5 
13 

7 
10 
12 
11 

80 
0 
0 
20 

8 
27 

0 
30 
0 
10 
0 
18 

20 
70 
100 
70 
92 
55 

Shank  broken  when  grain  was  in 
milk  stage  

Shank  broken  when  grain  was  in 
soft-dough  stage  ...           ... 

Stalk  broken  when  grain  was  in 
milk  stage  

Stalk  broken  when  grain  was  in 
soft-  dough  stage  

Ears  from  erect  plants  and  from 
unbroken  shanks  

lowest  percentage  of  "starchy"  individuals.  However,  as  may  be  seen 
from  Table  3,  the  chemical  composition  of  the  kernels  in  respect  to  the 
quantity  of  true  starch  which  they  contained,  did  not  harmonize  with 
their  physical  appearance. 

The  early  constriction  of  the  shanks  resulted  in  grain  high  in  total 
nitrogen,  hemicellulose,  and  crude  fibrous  material  that  was  non-hy- 
drolyzable  in  2.5-percent  hydrochloric  acid  and  low  in  ether  extract 
and  insoluble  starch.  When  the  breaking  of  the  shanks  was  delayed 
until  the  grain  was  in  the  soft-dough  stage,  the  proportion  of  total  ni- 


1926} 


INFLUENCE  OF  PLANT  INJURY  ON  COMPOSITION  OF  CORN 


265 


trogen,  hemicellulose,  and  non-hydrolyzable  material  was  not  so  high 
as  when  the  breaking  was  done  earlier,  but  it  still  was  considerably 
higher  than  in  the  normally  matured  ears.  There  was  also  a  signifi- 
cant increase  in  the  relative  amount  of  ether  extract  and  insoluble 
starch  as  the  grain  developed  from  the  milk  to  the  soft-dough  stage. 

The  breaking  of  the  stalk  did  not  affect  the  composition  of  the 
grain  so  much  as  did  the  constriction  of  the  shank,  altho  it  did  result 
in  a  slight  increase  in  total  nitrogen  and  non-hydrolyzable  material,  as 
well  as  in  a  small  decrease  in  ether  extract  and  insoluble  starch.  The 
time  of  breaking  the  stalks  had  very  little  effect  on  the  relative  quan- 
tity of  these  materials  in  the  grain.  It  appears  that  either  the  plant 
above  the  constriction  contained  a  sufficient  amount  of  previously 
elaborated  food  materials  to  fill  out  the  grain  to  an  almost  normal  de- 
gree, or  the  bending  of  the  vascular  elements  in  the  stalk  was  not 
acute  enough  to  prevent  the  passage  of  solutions  for  synthetic  pur- 


TABLE  3. — EFFECT  OF  THE  BREAKING  OF  THE  SHANKS  AND  STALKS  OF  CORN  ON  THE 

CHEMICAL  COMPOSITION  OF  THE  CORN  GRAIN 

(Amounts  expressed  in  percentages) 


Material 

Dextrins 

non-hy- 

3 

Total 

Ether 

Total 

and 

Insolu- 

Hemi- 

drolyz- 

Treatment 

nitro- 

ex- 

sugar 

solu- 

ble 

cellu- 

able  in 

O 

gen 

tract 

ble 

starch 

lose 

2.  5-  per- 

starch 

cent 

HC1 

A 

Parent  ears  

2.07 

4.83 

1.32 

2  01 

53.17 

6.62 

6.16 

B 

Shank  broken  when  grain  was 

in  milk  stage  

3.40 

3.  16 

1.  17 

1.76 

39.76 

9.55 

9.90 

C 

Shank  broken  when  grain  was 

in  soft-dough  stage  

2.27 

3.92 

1.54 

1.44 

44.71 

9.04 

7.68 

D 

Stalk  broken  when  grain  was 

in  milk  stage  

1.90 

4.  18 

1.05 

1.78 

51.85 

6.65 

6.19 

E 

Stalk  broken  when  grain  was  in 
soft-dough  stage  

1.85 

4.38 

1.53 

1.77 

51.61 

7.25 

6.81 

F 

Ears  from  erect  plants  and  from 
unbroken  shanks  

1.66 

4.56 

1.61 

2.67 

54.35 

6.66 

5.95 

poses  into  the  lodged  plant.  It  is  very  likely  that  both  the  transloca- 
tion  of  storage  material  already  in  the  stalk  and  the  deposition  of  re- 
serves synthesized  after  the  stalk  was  broken  were  contributing  factors 
in  producing  grain  of  a  practically  normal  composition.  Even  tho  the 
relative  amounts  of  materials  in  the  grain  produced  on  broken  stalks 
closely  approached  that  of  the  checks,  the  total  weights  of  ears  and 
grains  were  considerably  below  those  of  the  checks  (Table  1). 

A  comparison  of  the  data  presented  in  Table  2  with  that  in  Table 
3  brings  out  the  fact  that  the  condition  of  the  corn  grain  which  has  so 
often  been  described  by  the  term  "starchy"  is  not  necessarily  associ- 
ated with  a  higher  percentage  of  starch  in  the  grain,  but  that,  on  the 


266 


BULLETIN  No.  284 


[December, 


contrary,  there  is  a  slight  suggestion  that  the  ears  which  are  more 
"starchy"  in  appearance  may  actually  contain  less  starch  hydrolyzable 
with  saliva  than  horny  ears  of  the  same  variety. 

EFFECT  OF  PLANT  INFECTION  WITH  CORN  ROOT 
ROT  ORGANISMS 

Not  all  the  plants  that  were  inoculated  with  the  four  corn  root 
parasites  gave  evidence  of  being  injured  appreciably  by  these  organ- 
isms. In  order  to  obtain  data  on  the  effectiveness  of  the  inoculation, 
both  shelled  grain  weights  and  root  anchorage  figures  were  taken.  The 


TABLE  4. — SPECIFIC  GRAVITY  OF  THE  GRAIN  PRODUCED  FROM  INOCULATED  HILLS 

COMPARED  WITH  THAT  OF  GRAIN  FROM  PLANTS  IN  ADJACENT, 

UNINOCULATED  HILLS 


Number 
by  which 

Specific  g 
grain  f 

ravity  of 
rom  — 

Difference 

Organism  with  which  seed  was 
inoculated 

inoculated 
plant  was 
designated 

Inoculated 
hill 

Adjoining 
uninocu- 
lated 
hill 

uninocu- 
lated 
hill 

Diplodia  zeae  .    ...    

2b.. 

1.111 

1.116 

.005 

9b  

1.096 

1.042 

—  054 

27b  

1.085 

1.126 

.041 

37b  

1.132 

1.161 

.029 

55b  

1.053 

1.188 

.135 

Average.  . 

1.095 

1.127 

.032 

Fusarium  moniliforme  

3a.  . 

1.222 

1.302 

.080 

lOa  

1.217 

1.243 

.026 

28a.  .    . 

1.214 

1.245 

.031 

56a  

1.312 

1.302 

-.010 

3b  

1.090 

1.100 

.010 

lOb  

1.127 

1.117 

-.010 

•       :           f^J 

17b  

1.066 

1.040 

-  .026 

28b.  .. 

1.167 

1.196 

.029 

38b  

1.193 

1.298 

.105 

Average.  . 

1.178 

1.205 

.027 

Gibber  eUa  saubinetii  

54a.  . 

1.281 

1.293 

.012 

12b.  . 

1.047 

1.069 

.022 

19b  

1.142 

1.132 

-.010 

40b  

1.188 

1.239 

.051 

54b  

1.233 

1.320 

.087 

Average.  . 

1.178 

1.211 

.033 

Rhizopus  spp  

18a.  . 

1.243 

1.243 

.000 

25a  

1.173 

1.226 

.053 

4b  

1.063 

1.066 

.003 

25b  

1.040 

1.040 

.000 

32b  

1.219 

1.239 

.020 

Average.  . 

1.148 

1.163 

.015 

Grand  average  

1.154 

1.181 

.027  . 

Odds  that  the  average  difference  is  not  due  to  chance  =  302:1 


1926] 


INFLUENCE  OF  PLANT  INJURY  ON  COMPOSITION  OF  CORN 


267 


root  anchorage  was  determined  by  measuring  the  pulling  resistance  of 
the  hills  at  harvest  time.  Grain  from  only  those  plants  that  yielded 
less,  or  that  had  a  root  anchorage  below  that  of  the  adjoining  uninocu- 
lated  check,  was  selected  for  analysis.  The  yield,  however,  was  given 
primary  consideration  in  making  this  selection.  No  ear  was  taken  for 
this  study  unless  its  weight  was  less  than  its  check. 

It  was  possible  in  many  instances  by  visual  comparison  to  detect 
a  slightly  greater  proportion  of  soft  starch  in  the  corn  from  the  inoc- 
ulated hills.  This  was  not  possible,  however,  in  every  case.  In  order 
to  determine  more  accurately  the  influence  that  infection  had  upon 
the  density  of  the  grain,  specific  gravity  determinations  by  displace- 
ment in  95-percent  alcohol  were  made.  The  results  of  this  experiment 
are  given  in  Table  4. 

In  only  five  cases  out  of  the  twenty- four  sets  tested  did  the  grain 

TABLE  5. — PERCENTAGE  OF  WATER  ABSORBED  BY  GRAIN  PRODUCED  ON  CORN  PLANTS 

GROWN  FROM  INOCULATED  SEED,  COMPARED  WITH  THAT  ABSORBED  BY 

GRAIN  PRODUCED  ON  PLANTS  FROM  UNINOCULATED  SEED 


Organism-  with  which  seed 
was  inoculated 

Number 
by  which 
inoculated 
plant 
was 
designated 

Amount    of    water 
absorbed  in  24  hours 
by  grain  produced  on 
plants  from  — 

Difference 
in  favor 
of  corn 
from 
inoculated 
seed 

Inoculated 
seed 

Adjoining 
uninocu- 
lated  seed 

Diplodia  zeae  

27b.  . 

perct. 
72.53 
64.27 
67.82 
68.21 

perct. 
64.16 
63.09 
62.28 
63.18 

perct. 
8.37 
1.18 
5.54 
5.03 

37b  

55b  

Average.  . 

Fusarium  moniliforme  

3a 

53.09 
51.40 
55.41 
65.26 
61.32 
73.06 
54.87 
59.20 

49.26 
44.89 
49.42 
58.97 
62,57 
54.53 
47.86 
52.50 

3.83 
6.51 
5.99 
6.29 
-1.25 
18.53 
7.01 
6.70 

28a  

56a  

3b  

lOb.      . 

28b  

38b  

Average.  . 

Gibberella  saubinetii  

54a.. 
12b  

47.58 
72.03 
67.57 
62.91 
56.62 
61.34 

48.34 
63.12 
64.97 
54.66 
48.59 
55.93 

-    .76 
8.91 
2.60 
8.25 
8.03 
5.41 

19b  

40b  

54b  

Average.  . 

Rhizopus  spp  

4b. 

72.04 
56.99 
64.52 

65.04 
54.66 
59.85 

7.00 
2.33 
4.67 

32b  

Average.  . 

Grand  average  

62.04 

56.26 

5.78 

Odds  that  this  difference  is  due  to  inoculation  >  9999:1 


268 


BULLETIN  No.  284 


[December, 


from  the  inoculated  plant  exceed  that  of  the  check  in  specific  gravity. 
This  occurred  once  with  Diplodia,  three  times  with  Fusarium,  and 
once  with  Gibberella.  In  every  case,  however,  the  average  specific 
gravity  was  higher  for  the  corn  from  uninoculated  plants,  and 
when  the  results  from  all  the  organisms  were  averaged  the  grain  from 
uninoculated  plants  was  found  to  be  .207  higher  than  the  specific  grav- 
ity of  the  infected  plants,  with  odds  of  302  to  1  that  this  difference  was 
not  due  to  chance. 

In  some  previous  work  by  the  author8  it  was  shown  that  corn  pos- 
sessing a  high  proportion  of  soft  starch  in  the  endosperm  is  capable  of 

TABLE  6.— RESULTS  OF  CHEMICAL  ANALYSES  OF  CORN  GRAIN  PRODUCED  BY  PLANTS 

GROWN  FROM  INOCULATED  AND  FROM  UNINOCULATED  SEED 

(Results  expressed  in  percentages) 


Kind  of  corn 

Plant 
No. 

Total 
nitro- 
gen 

Ether 
extract 

Total 
sugar 

Dextrins 
and  solu- 
ble 
starch 

Insol- 
uble 
starch 

Hemi- 
cellu- 
lose 

Non-hy- 
drolyza- 
ble 
residue 

Diplodia-inoculated.  .  .  . 
Adjacent  check  

2b..  . 
6b.... 

2.77 
2.22 

4.26 
4.70 

1.32 
1.68 

2.58 
3.15 

48.22 
50.06 

7.72 
7.91 

5.94 
5.32 

Diplodia-inoculated.  .  .  . 
Adjacent  check  

9b... 
13b  

2.26 
1.81 

4.67 
4.61 

1.13 
1.39 

1.89 
1.75 

51.23 
52.92 

7.67 
7.36 

5.87 
6.49 

Fusarium-inoculated.  .  . 
Adjacent  check  

lOa.  .  . 
14a  

2.31 
1.99 

4.07 
4.42 

1.23 
1.53 

2.48 
2.67 

48.93 
51.30 

•6.13 
6  46 

4.52 
4.35 

Fusarium-inoculated.  .  . 
Adjacent  check  

17b... 
21b  

1.64 
1.84 

4.45 
4.74 

1  32 
1.34 

1.73 
1.82 

53.32 
53.21 

8.29 
7.53 

6.33 
5.95 

Gibberella-inoculated  .  . 
Adjacent  check  

la.. 
5a  

1.55 
1.68 

3.73 
4.12 

.95 
.95 

3.07 
2.43 

61.96 
55.76 

5.85 
5.91 

5.33 
5.56 

Gibberella-inoculated  .  . 
Adjacent  check  

Ib... 
5b..  .. 

2.92 
1.79 

4.44 
5.16 

1.03 
1.24 

2.71 
2.76 

45.65 
56.97 

8.16 
7.45 

7.76 
6.25 

Rhizopus-inoculated  .  .  . 
Adjacent  check  

ISa  
14a  

2.02 
1.99 

5.01 
4.42 

1.70 
1.53 

3.92 
2.67 

52.94 
51.30 

5.74 
6.46 

4.81 
4.35 

Rhizopus-inoculated.  .  . 
Adjacent  check  

25a  
21a.... 

2.37 
.2.09 

4.02 
4.38 

1.08 
1.13 

2.30 
2.43 

52.58 
55.28 

6.57 
6.79 

7.29 
4.70 

Rhizopus-inoculated.  .  . 
Adjacent  check  

25b... 
21b.... 

1.87 
1.84 

4.65 
4.74 

1.29 
1.34 

2.01 
1.82 

53.92 
53.21 

6.94 
7.53 

5.14 
5.95 

Average   difference   in 
favor  of  inoculated 
plant  

+     31 

—     22 

—     12 

+     13 

-1   14 

-   .14 

+   .45 

Odds  that  above  dif- 
ference is  not  due  to 
chance  

44:1 

57:1 

57:1 

4:1 

4:1 

5:1 

18:1 

more  rapid  water  absorption  than  corn  containing  a  less  amount  of 
this  material.  Accordingly,  the  water-absorptive  capacity  of  the  corn 
in  the  present  experiment  was  determined  with  a  view  to  applying  the 
results  as  a  measure  of  soft-starch  content.  The  data  included  in  Table 
5  were  obtained  by  soaking  samples  of  corn  produced  by  inoculated 
and  check  plants,  in  distilled  water,  under  the  same  conditions,  for  a 
period  of  twenty-four  hours.  The  percentages  are  based  on  the  water- 
free  weight  of  the  sample. 


1926} 


INFLUENCE  OF  PLANT  INJURY  ON  COMPOSITION  OF  CORN 


269 


In  every  instance  except  two — one  with  Fusarium  and  one  with 
Gibberella — the  corn  from  infected  plants  absorbed  more  water  than 
that  from  the  adjoining  checks.  When  all  the  determinations  with 
corn  from  plants  inoculated  with  the  four  organisms  were  averaged, 
the  difference  between  the  percentage  of  water  absorbed  by  the  grain 
from  inoculated  plants  and  that  by  grain  from  the  checks  was  5.78, 
and  the  odds  were  greater  than  9999  to  1  against  a  difference  as  great 
as  this  being  due  merely  to  chance. 

Notwithstanding  this  conclusive  evidence,  the  results  of  the  chem- 
ical analyses  of  representative  samples,  as  presented  in  Table  6,  do 
not  show  any  marked  differences  between  corn  grain  produced  by 
plants  from  inoculated  seed  and  those  from  uninoculated  seed. 

When  the  differences  between  the  two  types  of  grain  in  all  the  nine 
pairs  of  determinations  are  averaged,  it  is  found  that  the  corn  from 
the  inoculated  plants  contained  .31  percent  more  nitrogen,  .13  percent 
more  soluble  starch  and  dextrins,  and  .45  percent  more  non-hydroly- 
zable  substance  than  the  accompanying  checks.  The  odds  that  these 
average  differences  were  not  due  to  chance  were  44  to  1,  4  to  1,  and 
18  to  1,  respectively.  The  corn  from  the  uninoculated  plants  exceeded 
that  from  the  inoculated  plants  in  ether  extract  by  .22  percent,  with 
odds  of  57  to  1.  The  average  difference  in  total  sugar  was  .12  percent 
in  favor  of  the  uninoculated  checks,  and  this  result  also  carried  odds 
of  57  to  1.  Insoluble  starch  and  hemicellulose  averaged  slightly  higher 
for  the  check  corn,  but  the  significance  of  these  results  as  measured  by 
odds  is  very  low. 

CHEMICAL  CHANGES  OCCURRING  IN  "STARCHY"  AND  HORNY 
CORN  DURING  THE  GERMINATIVE  PROCESS 

A  preliminary  analysis  of  the  four  lots  of  Learning  corn  repre- 
sented in  Figs.  1  and  2  showed  that  the  "starchy"  lots,  B  and  D,  had 
practically  the  same  percentage  composition  as  the  horny  lots,  A  and 
C.  That  there  was  a  marked  difference  in  these  lots  of  corn  may  be 
seen  from  their  specific  gravity,  a  record  of  which  is  given  in  Table  7. 

TABLE  7. — SPECIFIC  GRAVITY  OF  THE  GRAIN  OF  LEAMING  CORN,  Two  LOTS  OF 
WHICH  WERE   HORNY  AND  Two   "STARCHY" 


Average 

specific 

Type  of  corn 

Lot 

Weight  of 
20  kernels 

Specific 
gravity 

gravity  of 
the  two  lots 

of  the 

same  type 

(grams) 

Horny  

A.. 

7.85 

1.312 

1.292 

C  

7.87 

1.271 

"Starchy"..   . 

B.. 

6.54 

1.208 

1.204 

D  

6.40 

1.199 

270 


BULLETIN  No.  284 


[December, 


In  order  to  obtain  data  on  the  difference  in  quality  of  the  mater- 
ials contained  in  these  two  types  of  seed,  a  germination  test  of  both 
was  made  at  16°  C.,  and  the  kernels  and  the  seedlings  with  grains 
attached  were  sampled  for  analysis  every  two  days.  The  degree  of 
development  is  illustrated  in  Fig.  4.  The  results  obtained  are  presented 
in  Table  8.  The  data  from  Lots  A  and  C  and  from  Lots  B  and  D 
are  averaged  and  set  forth  in  this  table  under  the  descriptive  heads, 
horny  and  "starchy,"  respectively. 

TABLE  8. — CHEMICAL  COMPOSITION  OF  THE  CoRfr,  GRAIN,  AND  SEEDLINGS  OF  HORNY 
AND  "STARCHY"  CORN  DURING  THE  PROCESS  OF  GERMINATION  AT  A 
CONSTANT  TEMPERATURE  OF  16°  C. 


Material 

Type  of 
corn 

Percentage  composition  of  seedlings  after  being 
on  the  germinator  for  different  numbers  of  days 

0 

days 

2 
days 

4 
days 

6 

days 

8 
days 

10 

days 

Ether  extract  

Horny.  .  .  . 
"Starchy"  . 

4.81 
4.96 

4.81 
4.95 

4.74 
4.87 

4.58 
4.64 

4.21 
4.31 

4.03 
4.00 

Total  nitrogen  .... 

Horny.  .  .  . 
"Starchy"  . 

1.94 
1.89 

1.94 

1.85 

1.94 

1.88 

1.93 
1.85 

1.90 
1.79 

1.91 
1.85 

Soluble  nitrogen.  .  . 
Total  sugar  

Horny.  .  .  . 
"Starchy"  . 

Horny.  .  .  . 
"Starchy"  . 

.24 
.25 

1.27 
1.26 

.19 
.20 

1.34 
1.26 

.21 
.24 

'  1.66 

1.27 

.33 
.35 

2.91 
3.00 

.41 

.42 

3.87 
3.42 

.53 
.53 

5.66 
6.10 

Reducing  sugar.  .  . 

Horny.  .  .  . 
"Starchy"  . 

.15 

.02 

.68 
.57 

1.47 
1.04 

1.84 
1.92 

2.53 
2.40 

3.71 
3.98 

Dextrins  and  solu- 
ble starch  

Horny.  .  .  . 

"Starchy". 

Horny.  .  .  . 

"Starchy"  . 

2.73 
2.90 

51.52 
50.91 

2.67 
1.92 

50.16 
50.45 

2.92 
2.52 

50.54 
50.82 

3.22 
2.41 

49.49 
50.06 

3.76 
2.64 

47.23 

47.78 

3.20 
2.45 

45.57 
46.48 

Insoluble  starch  .  .  . 

Hemicellulose  

Horny.  .  .  . 
"Starchy"  . 

6.96 
7.15 

7.12 
7.34 

7.13 

7.51 

7.10 

7.48 

7.26 
7.34 

7.35 

7.82 

From  the  second  day  to  the  end  of  the  period  there  was  a  grad- 
ual but  distinct  reduction  in  the  percentage  of  ether  extract  in  both 
the  horny  and  the  "starchy"  groups.  This  decrease  is  illustrated 
graphically  in  Fig.  5.  These  data  harmonize  with  the  results  obtained 
by  Toole,37  who  found  that  the  fat  in  the  maize  embryo  was  rapidly 
oxidized  during  the  germinative  process. 

The  fact  that  the  "starchy"  corn  possessed  a  slightly  greater  per- 
centage of  ether  extract  than  the  horny  ears  should  not  be  taken  as  of 
any  particular  significance,  for  the  "starchy"  Lot  B  contained  some- 
what less  fat  than  either  Lots  A  or  C.  Lot  D,  however,  was  abnor- 
mally high  in  fat,  and  this  contributed  to  the  slightly  superior  average 


INFLUENCE  OF  PLANT  INJURY  ON  COMPOSITION  OF  CORN 


271 


of  the  "starchy"  group  over  the  horny  group.  It  is  also  probable  that 
the  more  rapid  exhaustion  of  the  fat  of  the  "starchy"  kernels  is  of 
doubtful  import,  since  the  differences  between  these  percentages  are 
well  within  the  error  common  to  these  determinations. 

There  was  a  very  slight,  tho  fluctuating,  reduction  of  total  nitro- 
gen during  germination.    The  proportion  of  soluble  nitrogen,  however, 


FIG.  4. — APPROXIMATE  AVERAGE  GROWTH  OF  THE  SEEDLINGS 
TAKEN  FROM  THE  GERMINATOR  AT  TWO-DAY  INTERVALS 


5.00 


4.75 


4.50 


4.25 


4.00 


-  *>Sf-arch  y"  corn 
-Horny  corn 


Days  on  cferminator  at  /6"C 

FIG.  5. — PERCENTAGES  OF  ETHER  EXTRACT  IN  HORNY  AND  IN 
"STARCHY"  CORN  AT  DIFFERENT  STAGES  OF  GERMINATION 


272 


BULLETIN  No.  284 


[December, 


after  a  small  decrease  at  the  end  of  the  second  day,  increased  appre- 
ciably thereafter.  It  is  worthy  of  note  that  the  soluble  nitrogen  was 
consistently  higher  in  the  "starchy"  than  in  the  horny  corn.  When  the 
soluble  nitrogen  was  calculated  as  a  percentage  of  the  total  nitrogen, 
the  greater  solubility  of  the  nitrogen  of  the  "starchy"  type  of  corn  is 
more  strikingly  emphasized.  Fig.  6  was  prepared  from  such  a  calcula- 
tion. 


Percentage  of  nitrogen  that  was  water 
so/ub/e 
*  fe  <5  5  %  *< 

/' 

// 

~  IS1 

Tarchy"  corn 
•>rny  corn 

> 
/ 
/ 

f 

''A 

f     / 
*     / 
t      / 

H 

/ 
/ 

/ 
•      , 

/  / 

/      / 

/      / 
/     / 
/     / 
/     / 
/      / 
/     / 
»      / 

^ON 

^.x 

^** 

/ 

•)                   2                  4                  C                  6                 /<• 

Days  on   cjerminator  at  /6"C 

FIG.  6. — PROPORTIONS  OF  TOTAL  NITROGEN  THAT  WERE  WATER- 
SOLUBLE  IN  HORNY  AND  IN  "STARCHY"  CORN  AT  DIF- 
FERENT STAGES  OF  GERMINATION 

A  larger  quantity  of  the  nitrogen  contained  in  the 
"starchy"  corn  was  in  a  soluble  form  than  that  in  the  horny 
corn.  In  this  respect  the  "starchy"  corn  resembles  grain 
lacking  in  maturity.  There  is  the  suggestion  that  the  nitro- 
gen of  the  "starchy"  corn  is  more  readily  converted  to  the 
soluble  form  during  the  process  of  germination  than  is  the 
case  with  horny  corn. 


The  amount  of  total  sugar  in  the  horny  corn  increased  from  the 
very  beginning  of  germination.  The  rise  was  more  gradual,  however, 
during  the  early  than  during  the  later  stages  of  germination.  The  in- 
crease of  sugar  in  the  "starchy"  corn  was  initiated  somewhat  more 
slowly  than  that  in  the  horny  corn,  altho  at  the  end  of  the  sixth  day 
the  amount  of  total  sugar  in  the  "starchy"  corn  slightly  exceeded  that 


INFLUENCE  OF  PLANT  INJURY  ON  COMPOSITION  OF  CORN 


273 


in  the  horny  corn.    A  comparison  of  these  two  types  of  corn  in  respect 
to  total  sugar  content  may  be  made  from  Fig.  7. 

The  increase  in  reducing  sugar  was  much  more  marked  from  the 
very  beginning  of  germination  than  was  the  case  with  total  sugar.  At 
the  end  of  the  second  day,  when  the  total  sugar  was  increased  only  .07 


I 

c: 


"t! 
6 

5 
4 
3 
2 

0 
( 

Joto  '      \ 

—  —  Horni. 

/  corn 
hy  corn 

i 

[ 

Horntj 

i  corn 
-hy  corn 

/ 

/..- 

i               , 

i 

^. 

/ 

k  

^^ 

^/^ 

ir 

/ 

^ 

'"' 

924                6                8              /(. 
Days  on  germ/nator  af  /6°C 

FIG.  7. — PERCENTAGES  OF  TOTAL  AND  REDUCING  SUGARS  IN 
HORNY  AND  IN  "STARCHY"  CORN  AT  DIFFERENT 

STAGES  OF  GERMINATION 

There  was  no  uniform  difference  in  the  sugar  content 
of  the  horny  and  starchy  corn  during  the  process  of  ger- 
mination. On  the  6th  and  10th  days  of  germination  the 
percentages  both  of  total  and  of  reducing  sugars  were 
higher  in  the  "starchy"  corn  than  in  the  horny  corn.  The 
reverse  was  true  at  the  beginning  of  the  test  and  at  the 
end  of  the  2d,  4th,  and  8th  days  of  germination. 


of  one  percent  in  the  horny  corn,  and  not  at  all  in  the  "starchy"  corn, 
the  amount  of  reducing  sugar  was  multiplied  4%  times  in  the  horny 


274 


BULLETIN  No.  284 


[December, 


corn  and  28  times  in  the  "starchy"  corn.  Fig.  7  shows  that  the  rela- 
tion of  the  quantity  of  reducing  sugar  in  the  two  types  of  corn  was 
roughly  the  same  as  that  of  the  total  sugar.  It  is  evident  from  this 
chart  that  the  proportion  of  reducing  sugar  to  total  sugar  increased 
markedly  until  the  fourth  day  of  germination,  after  which  time  there 
was  a  reduction  in  this  proportion.  The  ratio  of  reducing  sugar  to  total 
sugar  approached  the  65-percent  mark  on  the  sixth  day  of  germination, 
and  remained  there  with  minor  variations  to  the  end  of  the  period. 

It  is  significant  that  the  soluble  starch  and  dextrins  were  consist- 
ently higher  in  the  horny  group  than  in  the  "starchy"  lot.  The  quan- 
tity of  these  materials  was  somewhat  greater  in  the  "starchy"  lots, 


So/ub/e  starch  and  dextrins 
in  percent 

^  I\J  Co  -t 

HA 

rny  corn 
jrchy'corn 

^ 

\ 

._"<?/; 

V- 

"^^ 

^ 

+ 

+**^^ 

„--'"'' 



0                 2                 4                 6                8                /t 

Days  on  germ/nator  at  /6'C 

FIG.  8. — SOLUBLE  STARCH  AND  DEXTRINS  IN  HORNY  AND  IN 
"STARCHY"  CORN  AT  DIFFERENT  STAGES 

OF  GERMINATION 

Soluble  starch  and  dextrins  are  intermediate  products 
in  the  conversion  of  starch  to  sugar.  Their  accumulation 
in  greater  quantities  in  the  horny  corn  during  germination 
is  suggestive  either  of  a  greater  ease  of  starch  hydrolysis 
or  of  a  less  rapid  utilization  of  the  final  products  of  hy- 
drolysis by  the  growing  seedling.  The  evidence  here  pre- 
sented indicates  that  the  former  is  nearer  the  truth  than 
the  latter. 


however,  at  the  beginning  of  the  germination  test.  The  uniform  con- 
tinuity of  this  greater  proportion  of  soluble  starch  and  dextrins  in  the 
horny  group  is  shown  in  Fig.  8. 

The  reduction  in  percentage  of  insoluble  starch  is  represented  in 
Fig.  9.  From  this  it  is  evident  that  the  digestion  of  starch  reserves  in 
the  endosperm  of  the  horny  grain  progressed  at  a  slightly  more  rapid 
rate  than  in  the  "starchy"  grain.  This  difference  in  unhydrolyzed 
starch  in  the  two  types  of  corn  is  in  accord  with  the  data  already  pre- 


1926} 


INFLUENCE  OF  PLANT  INJURY  ON  COMPOSITION  OF  CORN 


275 


sented,  showing  the  greater  proportion  of  soluble  starch  and  dextrins  in 
the  horny  than  in  the  "starchy"  corn.  Holbert  and  associates13  and 
Trost38  have  reported  that  the  seedlings  and  plants  produced  from 


51 


ft 


a 

<0 


47 


45 


-  "31-arch  y "  corn 
.Horny  corn 


8 


10 


Days  on  germinator  at  /6'C 

FIG.  9. — PERCENTAGES  OF  INSOLUBLE  STARCH  IN  HORNY  AND 
IN  "STARCHY"  CORN  AT  DIFFERENT  STAGES 

OF  GERMINATION 

Striking  as  it  may  seem,  the  horny  corn  contained 
slightly  more  starch  at  the  beginning  of  the  test  than  the 
"starchy"  corn.  From  the  2d  until  the  10th  day  of  germi- 
nation, however,  the  "starchy"  corn  contained  a  greater 
percentage  of  starch  than  the  horny.  This  suggests  that 
the  starch  of  the  horny  corn  is  more  readily  hydrolyzed 
to  soluble  forms  than  that  of  the  "starchy"  corn. 


seed  corn  having  a  horny  composition  were  superior  in  vigor  and  pos- 
sessed a  greater  resistance  to  certain  corn  diseases  than  seed  corn  hav- 
ing a  "starchy"  composition.  The  more  ready  solubility  of  the  starch  in 


276  BULLETIN  No.  284  [December, 

the  horny  endosperm  corn  than  in  the  "starchy"  corn  is  believed  to  be 
an  important  contributing  factor  to  this  difference  in  vigor  and  disease 
resistance. 

The  data  on  the  quantity  of  hemicellulose  fail  to  show  any  uni- 
form change  in  this  material  during  germination,  altho  on  the  whole 
it  did  increase  proportionately,  owing  in  all  probability  to  the  oxida- 
tive  consumption  of  other  carbohydrate  materials. 


DISCUSSION 

A  comparison  of  the  composition  of  the  grain  from  the  broken 
stalks  and  ear  shanks  in  the  present  experiment  with  the  results  ob- 
tained by  Hornberger  and  Raumer,15  Schweitzer,28  Jones  and  Huston,1* 
and  Smith32  shows  that  this  treatment  had  essentially  the  same  effect 
upon  the  grain  as  premature  harvesting.  There  was  an  increase  in 
starch  content  as  a  result  of  allowing  the  ears  to  remain  on  unbroken 
shanks  from  the  milk  stage  to  the  soft-dough  stage,  and  a  still  greater 
starch  deposition  when  the  ears  were  permitted  to  go  to  maturity  with- 
out shank  mutilation  (Table  3) . 

It  is  striking,  however,  that  in  those  samples  broken  at  the  inter- 
mediate stage,  the  physical  appearance  of  the  corn  was  such  as  to  be 
classed  as  100-percent  "starchy,"  whereas  those  ears  which  contained 
more  real  starch  were  apparently  not  so  "starchy"  (Table  2).  Further- 
more from  the  results  presented  in  Table  8  it  is  plain  that  corn  with  a 
high  proportion  of  soft  starch  in  the  endosperm  is  not  necessarily  high 
in  actual  content  of  starch.  There  is  evidently  a  physical  difference 
in  these  two  types  of  corn  which  represents  a  qualitative  dissimilarity 
as  well  as  a  quantitative  chemical  one. 

These  results  suggest  that  the  "starchy"  condition  may  be  induced 
or  accentuated  by  many  ecological  factors.  Interference  with  the  usual 
translocative  processes,  brought  about  by  breaking  the  stalks,  in- 
creased materially  the  proportion  of  soft  starch  in  the  endosperm. 
Premature  harvesting  doubtless  produces  the  same  effect.  The  injury 
to  the  shanks  which  greatly  increased  "starchiness,"  produced  an  effect 
not  unlike  that  of  complete  removal  of  the  ear  from  the  plant.  The 
modification  of  the  plant's  metabolism  caused  by  infection  with  the 
corn  root  rot  organisms  also  increased  the  "starchiness"  of  the  grain, 
and  the  root  rot  diseases  are  associated  with  both  hastened  and  de- 
layed maturity  of  the  grain.  It  would  seem  that  even  slight  altera- 
tions from  the  optimum  environment,  either  of  parasitic  or  climatic 
factors  and  possibly  edaphic  factors,  may  have  a  distinct  effect  upon 
the  quality  of  the  grain. 

Snyder33' 34  explains  that  the  light  weight  of  the  apparently 
"starchy"  wheat  grains  is  due  to  a  lower  than  average  degree  of  matur- 


1026]  INFLUENCE  OF  PLANT  INJURY  ON  COMPOSITION  OF  CORN  277 

ity,  as  evidenced  by  their  high  nitrogen,  phosphoric  acid,  and  potas- 
sium content. 

Roberts  and  Freeman  2fl  draw  the  conclusion  that  it  is  the  presence 
of  air-vacuoles  that  gives  to  yellow-berry  wheat  its  "starchy"  appear- 
ance and  its  uniformly  low  specific  gravity.  They  support  their  reas- 
oning by  stating  that  the  specific  gravity  of  starch  is  1.53,  sugar  1.60, 
and  cellulose  1.53,  whereas  gluten,  which  is  greater  in  amount  in  the 
horny  grain,  has  a  specific  gravity  of  only  1.297.  An  increased  amount 
of  a  substance  having  a  lower  specific  gravity  would  not  of  itself  in- 
crease the  specific  gravity  of  the  whole.  Hence,  it  was  assumed  that 
the  lesser  specific  gravity  was  due  to  air-vacuoles. 
,  Cobb4' 5  and  Lyon  and  Keyser23  point  out  that  the  starch  granules 
in  soft  wheats  are  larger  in  diameter  than  those  of  horny  wheats.  Even 
tho  the  horny  wheat  varieties  contain  some  large-sized  starch  gran- 
ules, their  relative  number  is  much  less  than  in  the  softer  varieties. 
Cobb5  also  notes  that  "whenever  the  starch  grains  are  large,  the  cells 
containing  them  are  also  large."  Lyon  and  Keyser23  working  with 
yellow-berry  in  wheat,  state  that  "the  protoplasmic  network  of  the 
cells  in  the  sections  from  the  very  horny  kernels  showed  only  an  oc- 
casional vacuole.  Sections  from  the  markedly  yellow  kernels  showed 
very  much  more  numerous  and  larger  vacuoles." 

Hackel11  attributes  the  filling  up  of  the  intervals  between  starch 
grains  to  albuminoids.  The  analyses  of  Hopkins,  Smith,  and  East14 
sup'port  this  view  by  showing  that  the  horny  starch  of  the  corn  grain 
contains  2.3  percent  more  protein  than  the  white  starch  of  the  same 
grain.  Their  data  also  show  that  the  horny  starch  contains  slightly 
more  oil. 

An  investigation  into  the  nature  of  the  starch  in  horny  and  in 
"starchy"  corn  would  seem  to  offer  a  very  promising  approach  to  the 
explanation  of  the  real  difference  between  these. distinct  types  of  dent 
corn.  Tanret,36  from  a  study  of  starches  in  oats,  bananas,  wheat,  chest- 
nuts, beans,  lentils,  maize,  barley,  peas,  apples,  rice,  buckwheat,  rye, 
and  potatoes,  concluded  that  the  starches  from  these  various  sources 
are  not  only  dissimilar  chemically,  but  that  they  react  differently  to 
physical  and  other  agents.  Since  the  various  grains  and  fruits  con- 
tain different  kinds  of  starch,  it  is  probable  that  there  may  be  man} 
different  kinds  of  starch  within  the  same  grain,  and  when  the  propor- 
tions of  these  vary  the  character  of  the  grain  is  changed. 

That  there  is  a  difference  either  in  the  ease  with  which  starch  is 
hydrolized  or  in  the  activity  of  the  dissolving  enzym  is  indicated  by 
the  consistently  superior  quantity  of  soluble  starch  and  dextrins  in 
the  horny  corn  over  the  "starchy"  corn  during  germination.  This 
property  is  in  all  probability  responsible  for  the  greater  vigor  of  corn 
seedlings  from  the  horny  seed.13 


278  BULLETIN  No.  284  [December,. 

The  immediate  problem  confronting  the  research  worker  in  this 
field  appears  to  be  not  so  much  the  question  of  what  factors  tend  to 
favor  the  development  of  the  "starchy"  character  of  corn  grain,  but 
what  "starchiness"  really  is  as  contrasted  with  horniness,  the  influence 
which  this  condition  has  upon  the  metabolic  processes  incident  to 
seedling  production,  and  the  ease  or  difficulty  with  which  seedlings  are 
infected  by  fungi. 

In  view  of  the  fact  that  the  difference  between  horny  and 
"starchy"  is  not  one  of  quantity  of  starch,  it  would  seem  desirable  to 
discontinue  the  use  of  the  term  "starchy"  as  descriptive  of  that  type 
of  corn  and  to  substitute  an  adjective  which  is  accurately  descriptive 
of  the  condition.  A  number  of  words  suggest  themselves,  but  cannot 
be  used  because  they  have  previously  been  adopted  to  describe  other 
conditions.  While  "soft"  is  often  used  to  carry  a  meaning  the  opposite 
of  horny,  common  usage  has  led  to  the  very  general  application  of  the 
term  to  immature  corn  having  an  unusually  high  percentage  of  mois- 
ture. The  adjective  "mealy"  would  be  a  good  term  to  substitute  for 
"starchy,"  but  it  has  been  used  by  Mangelsdorf24  to  designate  a  par- 
ticular type  of  endosperm  in  which  practically  all  the  material  of 
which  it  is  composed  is  soft  starch.  The  term  "floury"  is  therefore 
suggested  by  the  author  as  the  most  nearly  appropriate  word  for  de- 
scribing corn  grain  which  has  a  relatively  large  quantity  of  soft  starch 
in  the  endosperm.  "Floury"  connotes  the  qualities  of  flour;  namely, 
light  or  pale-colored,  soft,  and  powdery.  "Floury"  corn,  then,  wo'uld 
be  maize  grain  that  is  made  up  largely  of  material  having  a  pale  color 
and  a  soft  and  friable  texture.  The  distinction  between  "floury"  corn, 
as  it  is  understood  here,  and  the  flour,  or  soft,  corn  of  the  tropics 
should  be  kept  in  mind.  "Floury"  corn  is  corn  of  the  dent  type  pos- 
sessing a  relatively  high  proportion  of  soft  starch  in  the  endosperm, 
whereas  flour  corn  is  a  separate  and  distinct  type  of  corn,  the  grains  of 
which  are  very  large  and  the  endosperms  of  which  contain  no  horny 
material. 


CONCLUSIONS 

The  results  of  these  investigations  indicate  that  the  character 
of  the  starch  in  the  endosperm  of  corn  grain  may  be  influenced  to 
a  perceptible  degree  by  the  environment  in  which  it  is  produced.  The 
inoculation  of  the  seed  with  certain  organisms  capable  of  causing; 
the  corn  root  rot  disease  alters  the  physiology  of  the  plant  produced 
by  such  seed,  resulting  in  the  development  of  grain  containing  a 
greater  percentage  of  floury  starch  than  that  produced  by  plants  from 
uninoculated  seed.  Injury  of  the  plant,  such  as  the  breaking  of  the 
shanks  and  stalks,  before  the  grain  is  completely  mature  causes  an. 


1926}  INFLUENCE  OF  PLANT  INJURY  ON  COMPOSITION  OF  CORN  279 

increased  proportion  of  white  starch  in  the  grain  of  such  plants.  If, 
however,  the  shank  be  broken  when  the  ear  is  in  a  very  immature 
condition,  a  grain  possessing  a  waxy  rather  than  a  floury  endosperm 
may  result. 

Seedlings  produced  by  corn  possessing  a  relatively  large  quan- 
tity of  soft  starch  in  the  endosperm  are  not  so  vigorous  as  are  those 
from  horny  corn,  owing  to  the  fact  that  the  floury  starch  is  less 
rapidly  hydrolyzed  to  a  soluble  condition  than  the  horny  starch. 

In  general,  horny  corn  contains  as  much  starch  as,  and  fre- 
quently more  than,  floury  corn  of  the  same  variety,  but  the  specific 
gravity  of  floury  corn  is  much  lower  than  that  of  horny  corn. 

A  quantitative  determination  of  the  water  absorbed  by  different 
lots  of  corn  under  the  same  conditions  furnishes  a  good  index  as  to  the 
comparative  amounts  of  soft  starch  contained  in  the  samples. 

ACKNOWLEDGMENTS 

Grateful  appreciation  is  expressed  to  Doctor  E.  J.  Kraus,  Department  of 
Botany,  and  to  Doctor  J.  G.  Dickson,  Department  of  Plant  Pathology,  both  of 
the  University  of  Wisconsin,  for  the  interest  they  have  taken  in  this  problem 
and  for  the  many  helpful  suggestions  which  they  have  given  during  the  progress 
of  the  investigational  work  and  in  the  preparation  of  this  manuscript.  Dr.  W. 
E.  Tottingham,  of  the  Department  of  Agricultural  Chemistry,  also  of  the  Uni- 
versity of  Wisconsin,  has  assisted  by  suggesting  proper  chemical  methods,  and  to 
him  sincere  thanks  are  extended. 


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